The goal of this research is the elucidation of the molecular mechanism of an essential event in the mammalian fertilization, the sperm head membrane fusion and vesiculation known as the acrosome reaction. An in vitro hamster sperm system is used for these studies. Both the effect of exogenous molecules (hormones, serotonin and prostaglandin E2) and the role of sperm enzymes and stimulatory molecules (including the trypsin-like enzyme acrosin, phospholipase A2, an H+-pump ATPase, phosphatidic acid, arachidonic acid and its metabolites and cyclic nucleotides) are to be investigated. The methods to be used include in vitro incubation of sperm, gas chromatographic and HPLC separation of molecules of interest and biochemical assays for enzymes. In addition, assays will be made for the presence of serotonin and prostaglandin E2 in a putative site of the in vivo acrosome reaction, the cumulus oophorus. It is hoped that such studies will lead to a greater understanding of molecular basis of mammalian fertilization and thereby in the future lead to new contraceptive methodology and treatment for infertility based on this understanding.